The recovery of phenols from industrial waste liquor by suitable processes, and the treatment thereof with activated sludge containing certain microorganisms are already known.
Although in the past the waste liquor could be discarded after either one of the above-mentioned treatments, stricter regulations on waste water quality in recent years require further reduction in the content of substances in the treated water.
The waste water treatment with activated sludge has long been known and is already common practice in the industries. In certain cases, however, there is required a cultivation of particular microorganisms in large quantity since the microorganisms present in the activated sludge for general purposes are damaged by certain waste liquors. For example, free phenols which are extremely harmful to the active microorganisms present in the sludge are frequently found in the waste liquors from facilities for coke or coal gas production where the processes provide free phenols as by-products, facilities for phenol synthesis, facilities for producing phenolic resins and derivatives thereof, facilities for producing intermediates for dyes, agricultural chemicals, rubber modifiers, detergents and other industrial products, facilities for producing aromatic anti-oxidants and other additives, plywood manufacturing facilities and other facilities utilizing these materials in large quantities.
Certain phenols, for example cresol or phenol, are widely utilized for sterilization at a certain concentration, particularly by doctors. As is understandable from this fact, the free phenols in waste liquor from the aforementioned facilities, if there be a sudden surge in concentration for some reason and brought into direct contact with the activated sludge for general purpose, it will poison and kill the microorganisms present therein. Even if they are not killed immediately, the microorganisms maintained in prolonged contact with free phenols are gradually deprived of their activity and will die eventually.
Also waste liquors containing free phenols are generally acidic, or extremely alkaline if alkaline substances are employed for example as catalyst. Such waste liquors are not suitable for direct treatment with activated sludge for general purpose as the microorganisms present therein are known to be most active when maintained in contact with a waste liquor of neutral or weakly basic character. Although preconditioning in possible in such case, such preconditioning requires dilution of the waste liquor with a large amount of water, increasing the amount to be treated and resulting in a larger facility and a higher treating cost for industrial use. Also such preconditioning, involving microorganisms, is delicate and difficult to perform.
In order to treat such waste liquor containing free phenols by means of activated sludge there have been reported various attempts, such as:
(1) Decomposition by means of special domesticated microorganisms such as Trichosporon sp. red yeast (J. Nei, Hakko Kagaku Zasshi, 49 (8) 655 (1971) or Candida tropicalis (K. Ichikawa, Kogaku Kojo 17 (4), 77 (1973)); PA1 (2) Prolonged domestication of microorganisms in case of activated sludge for general use (H. Ono, Hakko Kogaku Zasshi 49 (4), 367 (1971)); PA1 (3) Resinification of free phenols by means of an alkaline substance as a pretreatment of waste liquor, eventually followed by addition of alkaline substance and centrifuging (S. Fukuoka et al., Hakko Kogaku Zasshi, 45 (2), 159 (1967)) etc.
These methods, though valuable as research methods, are not necessarily suitable for industrial use. More specifically, method (1) requires domestication of a large amount of microorganisms of of particular species with considerably cumbersome procedure, while method (2) cannot be used for immediate need, and method (3) is applicable only for particular phenols. Also the installation of a centrifuging facility and handling of the centrifuged material will require, in industrial scale, far greater efforts than in laboratory scale.